Question

Sickle cell anemia has not been eliminated from the African population because:

• A. it is controlled by recessive genes
• B. it is controlled by dominant genes
• C. it provides immunity against malaria
• D. it is not a fatal disease

Answer 1

The correct option is C

it provides immunity against malaria

The correct option is option C:

The explanation for correct option:

1. The malarial parasite grows inside the RBCs of the human body and derives nutrition from it.
2. The RBCs become sickle-shaped in sickle-shape anemia.
3. Hence the malarial parasite cannot survive in sickle-shaped RBCs and cannot survive.
4. Therefore in Africa where sickle-cell anemia is prevalent, it provides immunity against malaria.

The explanation for incorrect options:

Option A:

1. It is an autosomal disorder caused due to codominant genes.
2. The mutant gene which causes sickle cell anemia is Hb^S whereas the normal gene is Hb^A which produces normal hemoglobin.
3. Heterozygous persons with Hb^A/Hb^S genotype have both types of hemoglobin and suffer from sickle cell anemia.

Option B:

1. Sickle cell is caused by dominant genes however it is not the reason why in the African population it is not eliminated.
2. The malarial parasite cannot grow in sickle celled RBC hence it is not eliminated from the African population.

Option D:

1. The sickle cell RBCs clump together to block vasculature and cause severe anemia.
2. Due to anemia, the vital organs like the spleen, liver, and brain get damaged which leads to early death.

Final answer: Sickle cell anemia has not been eliminated from the African population because it provides immunity against malaria.